NECKING IN NONISOTHERMAL HIGH-SPEED SPINNING WITH RADIAL VISCOSITY VARIATION

This paper is a continuation and extension of previouS work by Ziabicki and Tian (J. Non-Newtonian Fluid Mech., 47 (1993) 57-75) on the necking phenomenon in non-isothermal high-speed melt spinning. The concept of flows with dominating extension as well as the possibility of radial viscosity variation, caused by temperature and orientation effects, have been taken into account. Under the assumption of the quasi-elongational approximation, various mechanisms of necking are discussed in greater detail. These are viscous, viscoelastic, inertial and, in particular, the radial viscosity mechanism. It is shown that, in general, any radial viscosity distribution across the filament intensifies the inertial mechanism. For sufficiently high radial viscosity variations a local reduction in axial velocity profiles is not necessary for the onset of necking.